Existing railroad locomotives are typically powered by diesel electric engines in which a diesel motor drives an electric generator to produce electric power to drive electric motors which in turn drive the drive wheels of the locomotive. The present inventor has disclosed the use of gas turbine engines fuelled by compressed natural gas in substitution for the traditional diesel engine in his U.S. Pat. No. 5,129,328 issued Jul. 14, 1992, and as a booster unit for the diesel engine in his U.S. Pat. No. 4,900,944 issued Feb. 13, 1990.
The use of electric batteries in combination with a heat engine is known for automobiles, buses and other road and highway vehicles. Such hybrid engines for vehicles are advantageous due to their increased fuel efficiency and reduced pollution. In those applications, it is important to minimize the weight of the batteries to maintain fuel efficiency. Electric batteries have been used to store electric power to drive electric locomotives. See Manns U.S. Pat. No. 1,377,087 issued May 3, 1921. In Manns, three standard diesel engines are used to drive generators to charge the storage batteries. Such a system has not achieved commercial acceptance over existing diesel electric locomotives due to the added cost and complexity of providing multiple diesel engines in addition to the storage batteries.
There is therefore a need for a fuel-efficient locomotive which uses a hybrid combination of storage batteries and a fuel-powered generator.